1. Field of the Invention
The present invention relates to an image developing apparatus and to an image forming apparatus using the image developing apparatus. More particularly, the present invention relates to an image developing apparatus and to an image forming apparatus, which prevent contamination of a charging roller or blocking of a light path by scattered toner during the developing process.
2. Description of the Related Art
An electrophotograph image forming apparatus forms an image on a recording medium, by use of an electrophotograph image forming method. The electrophotograph image forming apparatus may be an electrophotograph duplicator, an electrophotograph printer (for example, a laser beam printer), a facsimile and a MFP (multifunction printer).
The electrophotograph image forming apparatus such as the above-mentioned printer forms an electrostatic latent image by selectively exposing a photoconductive drum that is charged by a charging unit. The electrostatic latent image is developed with a developing agent in a developing unit. The image developed by the developing agent is scanned on the recording medium to record the image.
The electrophotograph image forming apparatus uses a process cartridge. The process cartridge may integrate the abovementioned charging unit and developing unit, or a cleaning unit and a photoconductive drum into one cartridge. This makes the cartridge attachable and detachable with respect to the image forming apparatus. Alternatively, at least one of the charging unit, the developing unit and the cleaning unit, and one photoconductive drum are integrated into one cartridge, and made attachable and detachable with respect to the image forming apparatus.
FIG. 1 is a fragmentary sectional view of a developing unit of a conventional image forming apparatus.
Referring to FIG. 1, a developing unit 10 includes an upper case 11 and a lower case 13. The inside of the upper case 11 is formed with a charging roller 15 and a photoconductive drum 17. The charging roller 15 charges a surface of the photoconductive drum 17 at a predetermined voltage, and the charged surface of the charging roller 17 is exposed to light irradiated from a light scanning unit 19, for example, a laser beam to form an electrostatic latent image on the surface of the charging roller 17.
The rear side of the upper case 11 is formed with a light passage hole (not shown) so that the light irradiated from the light scanning unit 19 can pass through and scan the surface of the photoconductive drum 17.
The inside of the lower case 13 includes a developing roller 21 for supplying toner to the electrostatic latent image formed on the surface of the photoconductive drum 17 and developing the latent image as a visible image. One side of the developing roller 21 is formed with a supplying roller 22 supplying the developing roller 21 with a toner (TI). An upper side of the lower case 21 has a regulating blade 23 regulating a toner layer of the developing roller 21, and the regulating blade 23 is supported by a blade bracket 25.
The abovementioned developing unit 10 operates as follows. The surface of the photoconductive drum 17 is charged through the charging roller 15 at a predetermined voltage. If a predetermined light is irradiated from the light scanning unit 19 on the charged surface of the charging roller 17 in the charged state, the electrostatic latent image is formed in the surface of the photoconductive drum 17.
The rotating surface of the developing roller 21 is supplied with the toner layer through the supplying roller 22. The toner layer is formed with a uniform thickness by regulating the thickness using a regulating blade 23.
The toner attached to the surface of the developing roller 21 moves to the photoconductive drum 17 by potential differences, and is applied on the electrostatic latent image to form a toner image. The photoconductive drum 17 and the developing roller 21 are not in contact, and positioned to provide a predetermined gap (D) therebetween. The toner formed on the surface of the developing roller 21 jumps the gap (D) between the photoconductive drum 17 and the developing roller 21, and moves to the photoconductive drum 17.
As discussed above, the photoconductive drum 17 and the developing roller 21 are not in contact, so the toner is not perfectly transferred, and the toner may be scattered. The scattered toner may contaminate the charging roller 15 and influence charging, thereby causing a defective image problem.
The scattered toner is attached to the upper side of the regulating blade 25, the inside of the upper case 11 or the external surface of the upper side of the lower case 13, and blocks a path of light irradiated from the light scanning unit 19, thereby causing image problems.